Parking brake driving me nuts!

[AirSpeed]

I can't get the parking brake to hold my truck on even the slightest incline. My brakes and all the components are in great condition, I adjusted them so they slightly drag, I adjusted the parking brake pedal so its solid at about 1/3rd the way down and they still won't hold. Everything behind the drum operates smoothly. I lubed the park brake cable and it all operates as it should but it still won't hold my truck even on flat ground. I have worked on plenty of brakes but this has me pulling my face off! Any ideas?
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[Lee H]

Assume you checked for brake fluid or oil soaked shoes and glazing. How about shoes in the correct location (primary VS secondary)?

[AirSpeed]

Originally Posted by Lee H

Are the shoes in the correct location front (primary VS secondary)?

Yes, they are in the correct position, they are about six months old and even when new they wouldnt hold the truck. My drums are in good shape as well. I can literally push the park brake lever with everything I got and they still won't hold. I took the drums off both sides and had my wife operate the p-brake lever while I watched the pads and they seem to operate correctly. They simply won't hold.
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[Lee H]

Are the shoes adjusted correctly? Is the cable tight when the parking brake pedal is hard, 1/3 the way down? If it is tight and no oil or glazing on the shoes or drums I would get out the shop manual and make sure all components are installed in the right location, orientation, etc. Something is a miss.

[cdowns]

rear cable in the cable housing rusted in place and not moving anything inside the brake drums is the rule rather than the exception

[AirSpeed]

Originally Posted by cdowns

rear cable in the cable housing rusted in place and not moving anything inside the brake drums is the rule rather than the exception

The cables operate all the parts they're supposed to, no rust and all the components are new. That's why it's driving me nuts! I even took the drums off my 69 to make sure I assembled everything correctly. I'm going to start fresh and replace it all again, fortunately brake parts are cheap! I'm tires of messing around.
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[AirSpeed]

Originally Posted by Lee H

Are the shoes adjusted correctly? Is the cable tight when the parking brake pedal is hard, 1/3 the way down? If it is tight and no oil or glazing on the shoes or drums I would get out the shop manual and make sure all components are installed in the right location, orientation, etc. Something is a miss.

Yep, the cables are bar tight when the pedal is pressed. I checked the working parking brake/brakes in my 69 to make sure I assembled it all correctly and all is well. I'm going to replace it all, I'm tired of messing around.
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[SS Tim]

Are the drums new or turned? If you turned the drums and the shoes were not arced you may have too a small contact area. While this may be workable with the service brakes the park brake may not generate enough pressure. This would be especially true if you are parked on an uphill grade trying to keep the truck from rolling backwards without the benefit of the self energizer. If this sounds like it might be the problem pull a drum and a shoe to verify the fit. Full contact is desirable and a high glazed spot would be worse case. Might also want to verify inside diameter of the drums as well. Also are you using a brake setting gage or guessing? Have you tried adjusting the rears off the ground in neutral?

[AirSpeed]

Originally Posted by Lee H

Are the shoes adjusted correctly? Is the cable tight when the parking brake pedal is hard, 1/3 the way down? If it is tight and no oil or glazing on the shoes or drums I would get out the shop manual and make sure all components are installed in the right location, orientation, etc. Something is a miss.

Well I just took another look at my brakes and I think I may have found the problem, I just noticed oil on the back side of the backing plate on one side, I didn't pay any attention to it before as all the components inside the hub are clean. I think my pads may in fact be coated in gear oil, there is a fine line dripping down towards the bottom of the drum, I think it's just enough to have ruined the pads at least on that side. I just called the parts store to see if they have the seals and new wheel bearings in stock (might as well put new bearings in there while I have the axles out!) and they gave me 7 different options of bearing/seal to choose from! I don't want to take it apart until I have the parts so I need to identify my axle. All I know is it's a 12 bolt, the parts guy wants to know if it has a lock ring holding the seal in plus a slew of other options! I had no idea there were so many variables in rear axles. My truck is a 72 GMC 1/2 ton short 4X4 with 350/350. I'm fairly sure now that this slight leak is my problem, either way I need to replace the seals anyway. If I can correctly identify my axle! Thanks!
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[AirSpeed]

Im now trying to ID my axle, I know it's a 12 bolt but the parts store wants more info in order to get the correct seals and bearings. First off this is a 72 GMC K1500 4X4, I found three sets of numbers, the first is on the upper left side of the diff housing, it reads "CN2". The next set is on the rear left axle tube which reads "1234", the 4 is questionable. The last set is on the lower left side of the diff and reads "678", the 6 in this case is also questionable.
The parts guy asked if the seal has a locking ring on it, I don't want to pull the axles until I have the parts as this is my daily driver. He's tellingly there are 7 different options as to what seals and bearings I may have. Anyone have any idea what axle I have?
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[leddzepp]

Aaron- Here are the seals you will need

National (Federal Mogul) part number is 8835S.
They measure 1.618 x 2.575 x 0.460

[AirSpeed]

Originally Posted by leddzepp

Aaron- Here are the seals you will need

National (Federal Mogul) part number is 8835S.
They measure 1.618 x 2.575 x 0.460

I picked some up yesterday, mine measure 1.42 X 2.512 X .323
I guess I will find out in a little while when I tear into the rear end. I'm replacing the bearings as well so I hope I got the correct ones otherwise my truck will be sitting on jack stands until tomorrow. Thanks!
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[leddzepp]

I also have a 72 12 bolt rear end. These were the seals I used. Yours should be the same. Good luck, this is definitely the reason your e-brake is not working!

[AirSpeed]

Originally Posted by leddzepp

I also have a 72 12 bolt rear end. These were the seals I used. Yours should be the same. Good luck, this is definitely the reason your e-brake is not working!

Looks like I have the wrong seals. I'm going to have them cross reference the part number you have and see what they come up with. Thanks!
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[AirSpeed]

Originally Posted by leddzepp

I also have a 72 12 bolt rear end. These were the seals I used. Yours should be the same. Good luck, this is definitely the reason your e-brake is not working!

I hope it's the problem, it's only leaking on one side and the leak is very slight but I can see now that it was enough to coat the brake pads, I'm replacing those as well.
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[Lee H]

Originally Posted by leddzepp

Aaron- Here are the seals you will need

National (Federal Mogul) part number is 8835S.
They measure 1.618 x 2.575 x 0.460

Same ones I used about a month ago.

[AirSpeed]

Originally Posted by leddzepp

I also have a 72 12 bolt rear end. These were the seals I used. Yours should be the same. Good luck, this is definitely the reason your e-brake is not working!

You were absolutely correct about the seals, unfortunately I don't get to use them because my axles were worn down where they ride in the bearing. I was going to buy a pair of new axles but a pair of repair bearings w/built in seals were only 1/4 the price! The repair bearings move the wear surface inward to a fresh area of the axles, I've never tried them before so I hope they work! I will have to wait until tomorrow morning as they didn't have any in stock.
The bearings that were in there looked like they were the originals, they had a snap ring on the inner and outer race that held the bearing cage in place. They were very, very pitted so I'm kinda glad I had problems with my brakes or I wouldnt have noticed how destroyed the bearings were. Any of you guys ever used these "repair bearings"? Do they work? I went ahead and bought new pads, the others had some very large cracks in them and were filled with gear oil. Brakes on, now I just have to wait till tomorrow morning to get the new bearings. Good excuse to exersize the 69 for a couple days! Thanks again! Aaron
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[AirSpeed]

Almost forgot, while I was pulling the old bearings I saw this strange item fall to the ground under the bed, I don't know where it fell from exactly but it landed in front of the rear axle. I was surprised anything could be under there cause I took the bed off the truck when I painted it, I don't know how I could have missed this thing. Anyway it's about 1 1/2" long with about a 5/8" hex head. It has very fine spiral threads from the very tip to the base of the hex head. I can't figure out what it is, I doubt it's part of the truck. Looks like a tool. Any ideas?

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[AirSpeed]

Got my new bearings this morning, the "repair bearings" and they worked great. I doubt I will ever have an issue with oil getting on the brakes now, the new bearings have two seals, one inner and one outer seal. It took a while to polish the new wear area on the axles but it was sure cheaper than a pair of new axles. Best of all I have a parking brake now and my brakes work better than ever.
Thanks again for the help! Aaron
P.S. anyone have any idea what the thing is in the above photo?
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[truckster]

I can't see the pic, but based on your description it sounds like the shaft of a gear puller.

[AirSpeed]

Originally Posted by truckster

I can't see the pic, but based on your description it sounds like the shaft of a gear puller.

Not sure, it has a very fine pointy tip that tapers up to the base of a hex shape nut, the hex part is about 5/8" tall and a 7/8" wrench fits it. My first thought was a sort of easy out tool but the threads go the wrong way. It looks really old by the amount of rust on it.
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[AirSpeed]

Now that my brakes are all pretty and new I am wondering exactly what the procedure is to activate the auto adjusting mechanism. I've always thought you need to back up and jam on the brakes to get it to turn the star wheel, then I have been told they adjust (if needed) every time you use the parking brake. Anyone have the straight poop on how they really work?
My brakes work better than ever now that I fixed the leaky seals. It's amazing how much damage so little gear oil can cause, the pads on the leaky side were cracked all over, deep cracks that went all the way through the pads. I'm guessing they were getting pretty hot even though they were soaked with oil.
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[SS Tim]

Looked it up in my '70 factory manual. It covers all 10-30 series trucks with the standard Duo-Servo brakes that I am pretty sure continued through '72.

"Brake shoe adjustment takes place when brakes are applied with a firm pedal effort while the vehicle is backing. Applying the brake moves an actuator which turns the star wheel and lengthens the adjuster screw assembly (fig.2)."

[AirSpeed]

Originally Posted by SS Tim

Looked it up in my '70 factory manual. It covers all 10-30 series trucks with the standard Duo-Servo brakes that I am pretty sure continued through '72.

"Brake shoe adjustment takes place when brakes are applied with a firm pedal effort while the vehicle is backing. Applying the brake moves an actuator which turns the star wheel and lengthens the adjuster screw assembly (fig.2)."

That's what I thought! Thanks for the confirmation!
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[Stocker]

Also (I found out the hard way) with the brakes assembled, you should reach through the slots in the backing plates -- with the brake tool -- and turn the star adjusters until the brakes start to drag. Then back them off a few turns. That gets 'em close, and they'll fine tune themselves as you back up & apply the brakes.